package threading;
//通过懒汉模式实现一下单例模式
class SingletonLazy {
    volatile private static SingletonLazy instance = null;

    public static SingletonLazy getInstance() {
        //这个条件，判断线程是否需要加锁，如果对象已经有了，就不必加锁了，此时线程本身就是安全的
        if(instance == null) {
            synchronized (SingletonLazy.class) {
                if (instance == null) {
                    instance = new SingletonLazy();
                }
            }
        }
        return instance;
    }
    private SingletonLazy() { }
}
public class ThreadDemo18 {
    public static void main(String[] args) {
        SingletonLazy s1 = SingletonLazy.getInstance();
        SingletonLazy s2 = SingletonLazy.getInstance();
        System.out.println(s1 == s2);


    }
}
